Telephone-exchange system



CL B. FOWLER TELEPHONE EXCHANGE SYSTEM Filed Sept. 8, 1920 2Sheets-Sheet 1 c. B. FOWLER.

TELEPHONE EXCHANGE $YSTEM Filed Sept. 8, 1920 2 Sheets-Sheet 2 fi n 1' 5Ta m- Z 1 1 N "a WW u.

Patented Jan. 13, 1925.

UNITED STATES PATENT OFFICE.

CLARENCE B. FOWLER, OF NEW YORK, N. Y., ASSIGNOR T WESTERN ELECTRIC COM-PANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEVT YORK.

TELEPHONE-EXCHANGE SYSTEM.

Application filed September 7 '0 all whom it may concern:

Be it known that I, CLARENCE B. FOWLER,

a citizen of the United States, residing at New York, in the county ofNew York and 6 State of New York, have invented certain new and usefulImprovements in Telephone-lilxchange Systems, of which the following isa full, clear, concise, and exact description.

This invention relates to telephone exchange systems and moreparticularly to such systems in which connections between telephonelines terminating at manual exchanges and telephone lines terminating atautomatic exchanges, are established by way of cord and trunk circuitsover which automatic switches are controlled from the manual exchangefor effecting connections.

The object of this invention is the production of improved talking andsignaling circuits for a system of this nature and also to provide forcomplete supervision over the connections for the operator at the manualexchange.

One of the features of the invention consists in providing a repeatingtrunk circuit with capacity which may be reduced to a lixed minimumunder the control of the 0pcrator to provide an efficient signalingcircult during the establishment of a connection, and increased to afixed maximum under the control of a called subscriber to provide anellicient talking circuit.

Another feature of the invention consists in such an arrangement ofcircuits and apparatus that the called subscriber not only controls thevarying of capacity to provide an eflicient talking circuit, but alsocontrols means for furnishing the operator with f l complete supervisionof the connection.

In the drawings Fig. 1 represents a circuit arrangement of asemi-automatic telephone exchange system embodying the invention, onlyso much being shown of the l5 circuits and apparatus as is necessary fora clear understanding of the present inventiou. Fig. 2 shows amodification of Fig. 1. There is shown in Fig. 1 of the drawings atelephone line A which terminates at the a: manual exchange where it maybe connected with a cord circuit B in any suitable and well-knownmanner. The calling end of the cord circuit may be connected with atrunk circuit T extending from the manual to the 8, 1920. Serial No.408,387.

automatic exchange, at which are provided the usual selector andconnector switches for effecting connection between the trunk circuitand telephone lines, such as D, ter minating at the automatic exchange.The apparatus shown to the left of the dotted line 1-1 is located at themanual exchange and to the right thereof at the automatic exchange. Thetrunk circuit T comprises inner and outer sections normally inductivelyunited by means of a large capacity condenser 14. A small capacitycondenser is normally disconnected from the trunk circuit, but it may beconnected to the trunk circuit under the control of the operator anddisconnected from the trunk circuit un der the control of the calledsubscriber such as D.

Referring to Fig. 2 of the drawings there is shown a telephone line Ewhich terminates at the manual exchange where it may be connected with acord circuit F in any suitable and well-known manner. The calling end ofthe cord circuit F may be connected with a trunk circuit T extendingfrom the manual to the automatic exchange. at which are provided theusual selector and connector switches for effecting connections betweenthe trunk circuit and the telephone lines, such as G, terminating at theautomatic exchange. The apparatus shown to the left of the dotted line2-2 is located at the manual exchange and that to the right thereof atthe automatic exchange. The trunk circuit T comprises inner and outersections normally inductively united by means of large capacitycondensers 121 and 124:. Small capacity condensers 122 and 123 arenormally disconnected from the trunk circuit T but may be connected tothe trunk circuit under the control of the operator and thendisconnected therefrom under the con trol of the called subscriber.

The nature of the invention'is suchthat it is believed a clearunderstanding thereof may be had from the following detailed description and the appended claims.

Referring to Fig. 1 of the drawings and assuming that the subscriber atthe station on the telephone line A has initiated a call, and that theanswering end of the cord circuit 13 has been associated therewith inany well-known manner, the operator actuates listening he; 5 therebyconnecting the operators telephone set (not shown) in circuit so thatthe operator may converse with the calling subscriber to ascertain thenumber of the line with which connection is desired. Ascertaining thatconnection is desired with telephone line D, which terminates at theautomatic exchange, the operator inserts calling plug 6 of the cordcircuit B into jack 7 of the trunk circuit T. Calling supervisory lamp 8of the cord circuit B is lighted over a path extending from groundedbattery, through lan l? 8,

resistance 10, sleeves otplug 6 andjack 7 and coil, 9 to ground.Relayf44 0i thetrunk circuit T operates over a circuit traceable 'lromgrounded rbattery, winding relay 44, left-handnormal contacts of relay-46, tips of jack 7 and plug 6, upper normal contacts of relay 22, uppernormal contacts or ringing key 42, and upper right-hand winding ofrepeating coil 50 to ground. The operation of relay 44 bridges polarizedrelay 13 in multiple with the non-inductive resistance 45 across thetalking conductors oi the outer section of the trunkover a pathtraceable from conductor 60, through. the winding ofpolarized relay 13in parallel with the back contact and armature of relay z-o andresistance 45 to conductor 61, "for he purpose of operating anon-numerical switch (not shown) at the automatic exchangeito extend thetrunk T to an idle connector C. As soon as the connection is "tended tothe connector C, line relay ereof is energized over a path extendingfrom grounded battery, left-hand winding cl relay 35, outer normalcontacts of relay so. conductor 61, front contact and armature of relay44, through resistance and righthand armature and back contact of relay46 in parallel with the winding of the polarized relay 13 to conductor60, inner normal contacts of relay 36, and right-hand winding ot' relay35 to ground. Polarized relay 13 does not operate at this time since thedirection of flow of current through its windings is such as to preventits operation.

The operator may now actuate the impulse sender S, which is common tothe cord circuits of her position. Upon the initial actuation of theimpulse sender S, the off normal contacts 21 thereof close, causing theoperation of relay 25 which remains uptl'itliBCl during the transmissionof each series of impulses. Relay 25 in operating, causes the operationof connecting relay 22 ot' the cord circuit B and switching relay '1 lotthe trunk circuit T over a circuit traceable from ground, armature andbackcontact of relay 23, front contact and left hand armature of relay25, outer lower contacts of key 5, lower normal contacts of key 42,inner lower normal contacts and winding of relay 22,, rings of plug 6and jack 7, armature and back contact of polarized relay 18, and Windingof relay 11 to grounded battery. Relay 22 in operating locks up inseries with relays 23 and 11 over a pathtraceable from ground, windingof relay 23, contacts of key 26, lower inner armature and front contactand winding of relay 22, rings of plug 6 and jack 7, armature and backcontact of polarized relay 13 and winding of relay 11 to: grounded battery. The operation of relay 22 opens the talking conductors of thecord. circuit B and connects groundthrough the impulse contacts 20 ofthe sender S to relay 44 to hold said relay 44, which was previouslyenergized, operated. the pilot relay 23 resulting from closure oi Theenergization of the locking circuit 01 relay 22, opens a contact in theoriginal energizing circuit oi relay 22 and causes lamp 28 to be lightedindicating to the operator that the impulses sendcr S has beenrenderedindividual to the cord circuit and connected therewith. As soonas pilot lamp 28 lights the operator may restore key 5 to normal.

The operation of relay 11 disconnects the large capacitycondenser 14from the talking conductors of the trunk circuit T and connects thesmall capacity condenser 15 there to, so that the large capacitycondenser will not interfere with the transmission oi iuipulses andstill provide a path for the trausmission oi? tones from the automaticexchange back to the calling subscriber as well as to the operator.Relay 22 ot the cord circuit and relay 11 of the trunk circuit afterbeing operated remain locked up until released by the operator actuatinkey 26 or until polarized relay 13 energizes upon the response of thecalled subscriber.

The opening and closing of the impulse contacts 20 of the sender Sduring the return movement of the sender to its normal positioncausesthe opening and closing of the circuit of impulse repeating relay44. Each time relay 44 deenergizes in response to the opening of itscircuit, the bridge across the outer section of the trunk circuit Twillbe interrupted thereby causing the deenergization of impulse relay35 of the connector C. The impulse relay of the connector controls theusual motor magnets tor the connector whereby the brushes 38 and 39 oi?the connector are set upon the terminals and iii of the telephone lineD. The subscriber at station l) may be signaled in a manner well knownin the art.

Tones,indicating to the calling subscriber that a station is beingsignaled or in case the calling line D had been busy and a source ofbusy tone had been connected to the trunk conductors and (S1 in anymanner well known in the art will be trans mitted to the callingsubscriber or to the operator even though the talking conductors of thetrunk and cord. circuit are opened, over a path traceable from conductor61 through the trout contact and armature of relay a l, lower alternatecontacts of relay 11, small capacity condenser 15 rings of jack 7 andplug 6, condenser l lower normal contacts of ringing key 42, and thenceto the operators telephone set or through the winding of supervisoryrelay 4i and lower right-hand winding of repeating coil to groundedbattery. The tone passing through the secondary winding of repeatingcoil 50 is induced into the primary winding thereof and passes throughsupervisory relay 56 over the line loop of line A to the subscribertherealx The operator and. the calling subscriber are thus supplied witha path for the reception of tones from the distant exchange. which isindependent of the normal tz'ilking conductors extending from saidsubscriber to said distant exchange.

The subscriber of telephone'line D in responding to the calling signalcauses the energization of reversing relay 36. The enen gization ofrelay 3(3 reverses the battery con llQClllOl'iS of the talkingconductors of the trunk circuit whereby polarized relay 13, bridgedacross the outer section of the trunk circuit '1, is energized and opensits back contact. The opening of this contact interrupts the lockingcircuit ol relays 23, 22 and 11. whereupon these relays deenergize. Thedeenergization of relay 2 opens the circuit of and extinguishes pilotlamp 28; the deenergization of relay 22 disconnects the sender S fromthe cord circuit B, renders the talking conductors of the cord circuitcontinuous, and short-circuits condenser l; and the deenergization ofrelay ll disconnects the small capacity condenser 15 front and connectsthe large capacity condenser l4: to the talking conductors of the trunkcircuit T.

The energization of polarized relay 13 also bridges relay 46 across thetalking conductors of the inner section of the trunk thereby causing theoperation of supervisory relay ll. of the cord circuit B over a circuittraceable from ground, upper righthand winding of repeating coil 50,upper nori'i'ial contacts of relay 22, tips of plug 6 and jack '7,winding of relay 46, front contact and armature of polarized relay l3,rings of jack 7 and plug 6, back contact and lower outer armature ofrelay 22, lower normal contacts of ringing key 42, winding ofsupervisory relay ll, and lower right-hand winding of repeating coil 50to grounded battery. Relay 41 in energizing shunts supervisory lamp 8,thereby causing the ex tinguishing oi? said lamp, which indicates to theoperatorthat the called party has responded.

Relay 4:6 is energized over the circuit ust traced and in attracting itsleft-hand armature, substitutes a local ground for main taining impulseresponsive relay lt in place of the ground at the contacts 20 of impulsesender S, and in attracting its right-hand armature removes thenon-inductive resistance l5 from parallel relationship with the windingof poralized relay 13.

Prior to the response of the called subscriber at the telephone line D,the operator may tree the impulse sender S from connection with the cordcircuit B by actuating key 20. Opening of the contacts of the key 26interrupts the locking circuit for relays 23, 22 and 11 in the mannerbe'tore described, thereby disconnecting the sender S from the cordcircuit; rendering the talking conductors of the cord circuitcontinuous;

substituting the small for the large capacity condenser; andextinguishing pilot lamp 28. If, after the operator actuates the key 26,the subscriber of station D responds by removing the receiver from theswitchhook, the energization of reversii'ig relay 36 causes theoperation of polarized relay 13. The operation of relay l3 bridges relayl6 across the talking conductors of the inner section of the trunk,whereupon supervisory relay ll-l energizes thereby extinguishing thesupervisory lamp 8.

At the conclusion of conversation the subscribers restore theirreceivers to the switchhooks. The restoration of the receiver to theswitchhook at the station on the elephone line D, causes thedeenergization of reversing relay 36, whereupon the connection ofbattery and ground with the talking conductors of the trunk circuit isreversed causing the release of polarized relay 13. Relay 4:6 is removedfrom bridged relation with the talking conductors otthe inner section ofthe trunk and supervisory relay ll deener-' gizes, permitting thelighting of the supervisory lamp 8 which now serves as a disconnectsignal to the operator at the manual otlice. The operator may thereupon(llSCOTlnect the plug 6 from the jack 7 whereupon all apparatusassociated with the calling end of the cord circuit 8 of the trunkcircuit T is released and restored to normal position, thereby releasingthe switches at the automatic exchange.

Referring tOl Fig. 2 of the drawings and assuming that the subscriber attelephone line E has initiated a call and the answering end of the cordcircuit F has been asso ciated therewith in any \-:ell-knov.u'i manner,the operator actuates a listening key (not shown) thereby connecting theoperators telephone set (not shown) in circuit so that the operator mayconverse with the calling subscriber to ascertain the number of the linewith which connection is desired. Assuming that connection is desiredwith telephone line (i. the operator may restore the key to normal andthen insert calling plug 106 of the cordcircuit F into jack 107 of thetrunk circuit T Relay 11.5 01 the cord cir cuit 1* and sleeve relay 120of the trunk circuit T are thereupon energized over a path extendingfrom grounded battery, through the winding of relay 115, winding ofmarginal relay 112 which is not energized at this time, normal contactsof relay 114:, sleeves of ph'ig 106 and jack 107 and winding of relay120 to "ground. Relay 115 in operating disconnects the usual test leadto the ope "ators telephone set from the tip of the cord circuit "andrenders the talking 'conductors'oi' the cordcirtuit conti'iuious. Relay1.12 is ot the in'argi'naltype and does not operate in series "withrelay 120, whichhas a high resistance armature of relay 126.

' winding.

'l'ni 'iedance coils 1'09 and 11.0 there'tore remain bridged across thetalking conductors of the cord when a connection established with thetrunk circuit 1. "he particular cord circuit herein shown adaptable foruse with other trunk circuits which do nothave a resistance such as thewinding of relay 120 connected to the sleeve 01 the ack in which case,the marginal relay 112 operates thereby disconnecting the impedancecoils 109 and from bridged relationship with the cord circuit. Relay inoperating establishes a circuit for the 'energiz ation 0tslow-to-release relay 118 over a path extending from grounded battery,through the inner armature and front contact of relay 120 and throughthe windingot relay 118 to ground. Relay 120 in operating also bridgesthe winding of polarized relay 126 across the outer section of the trunkthereby causing the operation of a non-numerical switch (not shown) atthe automatic exchange for the purpose of extending the trunk to an idleconnector switch such as K at the automatic exchange.

Impulses relay 128 at the connector K thereupon operates over a pathextending from grounded battery, left-hand winding of relay 128, outerleft-hand normal contacts of relay 129, conductor 131, outer right-handarmature and front contact of relay 120, winding of polarized relay 126,conductor 130. inner normal contacts of relay 129 and right-hand windingof relay 128 to ground. Polarized relay 128 does not operate at thistime since the direction of flow of current through its winding is suchas to prevent its operation.

The operation of slow-to-release relay 118 causes the operation ofrelays 116 and over a path extending from grounded battery, left-handarmature and front contact of relay 118, windings of relay 11.6 and 125in parallel to ground at the baclrcontact and Relays 116 and 125 inoperating disconnect the large capacity condensers 121 and 1.211 fromthe tip and ring talking conductors of the trunk circuit T respectively,andconnect the small capacity condensers 122 and 123 thereto. Relay 116in operating also connects ground and battery to the tip and ringtalking conductors of the inner section of the trunk circuit Trespectively, thereby causing the operation of supervisory relay 108 ofthe cord circuit over a path extending from ground, left-hand winding ofretardation coil 117, upper alternate contacts o't relay 116, tips 01jack 107 and plug 106, arn'iature and trout contact-of relay 115, coil110, baclr contact and armature ofrelay 112, winding of relay 108, coil109, rings ofplug 106 and jack 107, lower alternate contacts 01 relay116, and rightdiand winding ofre-tardatiou coil 117 to grounded-battery.Rtelay 1.08 in operating completes a circuit at its arinature and frontcontact tor the lighting of supervisory lamp 111. Relay 125 ol the trunkcircuit T in operating bridges non-- inductive resistance 12'? acrossthe outer section of the trunk in parallel with the winding of polarizedrelay 1267 The operator may now actuate the monitoring and dialing key105, which is pro vided for each of the cord circuits, 1 in addition tothe listening key therefor, heretot'ore referred to upon actuation ofkey 105, relay 11s v is energized over a path extending from ground,through contacts 101 ct 'ey 105 and, winding of relay 11st to ground dbattery. "lelay 1141, in operating, coiniecls the impulse sender S tothe sleeve the cord circuit through its inner armature and front contactand connects ground thro gh resistance 113 at its outer armature and t:out contact to relays 112 and 115 in order to hold relay 115 energized.

The operator may now actuate the inipulse sender S in order to set thebrushes oi switch K upon the terminals of the desired telephone line G.Each interruption of the contacts 1-10 of the impulse sender s causesthe release of repeating relay 120 oi the trunk circuit T which inretracting its armatures opens the bridge across the outer section ofthe trunk, thereby releasing impulse responsive relay 128 of thecoimector K. Relay 118 being slow-to-release does not retract itsarmature during the seiuling of a series of impulses and relays 11.6 andare tl'iereli y maintained energized. The impulse responsive relay 128of the connector switch K controls the usual motor magnets for theconnector at the automatic exchange under the control of which thebrushes 138 and 139 of the connector K are set upon the terminals and151 of the telephone line G. The call hell at the station of telephoneline G may be actuated in the usual nianner'and the subscriber in.responding to the operation thereof, removes the re ceiyer "from theswitchhook causing the energization of reversing relay 129. The enerill)lilu

gizat-ion of relay 129 reverses the battery connections to the talkingconductors oi the trunk circuit, whereby polarized relay 126, bridged.across the talking conductors of the trunk circuit T is energized andopens its contact. The opening of this contact interrupts the lockingcircuits for relays 116 and 125. Relays 116 and 125 thereupon release.Relay 116 in retracting its armatures renders the talking conductors ofthe trunk circuit T continuous, thereby disconnecting the small oapacity condensers from the trunk circuit and connecting the large capacitycondensers 121 and 124lthereto. Relay 116 in retracting its armaturesalso disconnects ground and battery from the tip and ring talkingconductors of the inner section 01 the trunk circuit T thereby causingthe release of supervisory relay 108 of the cord circuit- F and theconsequent extinguishing of the supervisory lamp 111, which indicates tothe operator that the called party has responded. Relay 125 in releasingremoves the non-inductive resistance 127 from parallel relationship withthe winding of polarized relay 126 and disconnects the small capacitycondensers 122 and 123 from the talking conductors of the outer sectionof the trunk circuit- T Up until the time that the called subscriber oftelephone line G responds, a path for tones, such as a busy signal tone0 a ringing signal tone exists over the trunk circuit '1 and theconnected cord circuit F for the operator and the calling subscriber orthe telephone line E over a path traceable from conductor 131, throughthe lower armature and front contact of relay 125, condenser 123, loweralternate contacts of relay 116, rings of jack l0? and plug 106 andthence through the calling substation loop or the operators telephoneset, to the front contact and armature of relay 115, tips of plug 106and jack 107, upper alternate contacts of relay 116, condenser 127,upper alternate contacts of relay 125 to conductor 130. The operator andsubscriber are thus supplied with a path for the reception of tones fromthe distant exchangewhich is independent of the normal talking circuitsextending from said subscriber to said. distant ex change.

At the conclusion of conversation the subscribers restore theirreceivers to the switchbooks. The restoration of the receiver to theswitchhook at the station of telephone line G causes the deenergizationof reversing relay 129, whereupon the connections of battery and groundwith the talking conductors of the trunk circuit are reversed causingthe release of polarized relay 126. Relay 126 in deenergizing againcompletes a circuit for relays 116 and 125 over paths previously traced.Relay 116 in operating connects ground and battery to the talkingconductors of the trunk circuit, thereby causing the energization ofrelay 108 as before described and the consequent lighting of supervisorylamp 111, which now serves as a disconnect signal to the operator at themanual oilice. The operator will thereupon disconnect the plug 106 fromthe jack 107, whereupon all apparatus associated with the calling end ofthe cord circuit F and with the trunk circuit T is released and restoredto normal position. Opening of the bridge across the outer section ofthe trunk circuit T causes the release of the switch at the automaticexchange.

What is claimed is:

1. In a telephone exchange system, a called line, an operators cordcircuit, a trunk circuit and automatic switches for estahlishing aconnection with said line, capacity in said trunk circuit, a supervisorysignal in said cord circuit, means controlled by the operator i orvarying said capacity, and

ieans controlled by the called line for varying said capacity and foractuating said signal.

2. In a telephone exchange system, a 02.11 ing line at a manualexchange, a called line at an automatic exchange, means including anoperators cord circuit, a trunk circuit and automatic switches forestablishing a connection between said lines, capacity for said trunkcircuit, and means controlled by the operatorand the subscriber of thecalled line for varying said capacity.

3. In a telephone exchange system, a called line, a trunk circuit, meansincluding an impulse sender and automatic switches for establishing aconnection over said trunk circuit with said line, capacity in saidtrunk circuit, means responsive to the actuation ol the impulse senderfor varying said capacity and means controlled by the called line forvarying said capacity.

4:. In a telephone exchange system, a trunk circuit, a cord circuitconnected therewith, an impulse sender, means responsive to theactuation of said sender for connecting it with the cord circuit.capacity in said trunk circuit, a telephone line, and a relay in saidtrunk circuit for varying said capacity and for causing thedisconnection of said sender from said cord circuit, said relay beingcon trolled by said telephone line.

5. In a telephone exchange system, a trunk circuit, a cord circuitconnected therewith, an impulse sender, means responsive to theactuation of said sender for connecting it with the cord circuit, atelephone line, a supervisory signal in said circuit, capacity in saidtrunk circuit, and means controlled by said telephone line fordisconnecting said sender from said cord circuit, actuating saidsupervisory signal and varying said capacity.

6. In a telephone exchange system, a Cord circuit, a called line, meansincluding a twoconductor trunk circuit for establishing a connection tosaid called line, a large capacity condenser normally connected in saidtrunk circuit, a small capacity condenser normally discoi'inected fromsaid trunk circuit, means controlled by said sender for substituting thesmall for the large capacity coi'idenser, and means controlled by saidcalled line for substituting the small for the large capacity condenser.

T. in. a telephone system, a calling line, a called line, meansincluding an operators cord circuit, a repeating trunk circuit havinginner and outer sections and automatic switches for establishing aconnection be tween said lines, an impulse sender for said cord circuit,condensers of large capacity normally connecting the inner and outersections of said trunk circuit, small capacity condensers normallydisconnected li'rom the inner and outer sections of said trunk circuit,operator controlled means for disconnecting said large capacitycondensers from said trunk circuit and substituting therefor said smallcapacity condensers, and means controlled by saidcalled line fordisconnecting said small capacity condensers and substituting said largecapacity condensers therefor.

S. In a telephone system, a calling station, a called station, meansincluding a link circult and a trunk circuit for interconnecting saidstations, capacity in said trunk circuit, means responsive to theconnection of the link circuit With the trunk circuit for varying thecapacity of the trunk circuit, and means controlled by the calledsubscriber for varying the capacity of the trunk circuit.

5,). In a telephone system, a calling station, a called station, meansincluding a cord circuit terniinating in a plug and a trunk circuitterminating in a jack for interconnccting saii'd stat-ions, capacity insaid trunk circuit, means responsive to the connection 01 the plug ofthe cord circuit With the jack oi the trunk circuit for varying thecapacity of the trunk circuit, and means automatically operating inresponse to the answering ot the called subscriber to again Vary thecapacity oi the trunk circuit.

In witness whereof, I hereunto subscribe my name this26th day of August,A. D., 1920.

CLARENCE B. FOWLER.

